Operational input control mechanism

ABSTRACT

An electromagnetic actuating device controls functional operations in a keyboard printer. In the printer, movement of each operational interposer is controlled by a lightweight armature plate having an adjustable actuating rod which when the electromagnetic means for each armature plate is energized will operate upon the end of an interposer to release the interposer to perform a selected functional operation in the printer, such as, &#39;&#39;&#39;&#39;tab,&#39;&#39;&#39;&#39; &#39;&#39;&#39;&#39;backspace,&#39;&#39;&#39;&#39; &#39;&#39;&#39;&#39;space,&#39;&#39;&#39;&#39; &#39;&#39;&#39;&#39;index&#39;&#39;&#39;&#39; or &#39;&#39;&#39;&#39;return&#39;&#39;&#39;&#39;; and, when deenergized, the armature plate will follow the return movement of the interposer to its original disposition in preparation for the next functional operation without the aid of a special return mechanism.

United States Patent [1 1 Becker [451 Aug. 7, 1973 1 OPERATIONAL INPUTCONTROL MECHANISM [75] Inventor: Harold D. Becker, Riverton, Wyo.

[73] Assignee: Datel Corporation, McLean, Va.

[22] Filed: Oct. 22, 1970 [21] Appl. No.: 82,896

3,294,117 12/1966 Eichemeyer et al.

3,082,854 3/1963 Becker et al 197/19 3,233,715 2/1966 Flieg 197/193,391,774 7/1968 Greer 197/19 12/1968 Knudsen et all. 197/20 7/1969Twardzik 197/19 [57] ABSTRACT An electromagnetic actuating devicecontrols functional operations in a keyboard printer. In the printer,movement of each operational interposer is controlled by a lightweightarmature plate having an adjustable actuating rod which when theelectromagnetic means for each armature plate is energized will operateupon the end of an interposer to release the interposer to perform aselected functional operation in the printer, such as, tab, backspace,space, index or return; and, when deenergized, the armature plate willfollow the return movement of the interposer to its original dispositionin preparation for the next functional operation without the aid of aspecial return mechanism.

4 Claims, 5 Drawing Figures PAIENIEDMIB m I 3150.193

INVENTOR HAROLD D BECKER ATTORNEYS OPERATIONAL INPUT CONTROL MECHANISMThis invention relates to a novel and improved mechanism forautomatically selected different functional operations to be performedin a business machine, and more particularly relates to anelectromagnetic actuat ing device for electrically controllingfunctional operations in a keyboard printer, typewriter and the like.

In the keyboard printer art, it is customary to employ a combination ofmanual and automatic actuating means for selectively releasing anoperational interposer to perform a given functional operation. Typicalfunctional operations in a keyboard printer include tab," backspace,space, index, and return. Commonly, the interposer or other linkageelements for each operation includes a releasable latch which normallyretains the interposer elements in a normally inoperative or lockedposition; and the manual or automatic actuating means is engageableeither with the latch or interposer to unlatch the interposer to performa selected operation. In accordance with the present invention, theautomatic actuating means is engageable at the end of the interposer orlatch member in order to effect maximum leverage and in such a way as toaccurately follow return movement of the interposer to its latchedposition without the use of separate return means; further, theautomatic actuating means is made up of a minimum number of partsoccupying the least amount of space and each actuating means is readilyadjustable and capable of direct positive actuation of the interposerwith which it is associated.

It is therefore an object of the present invention to provide novel andimproved automatic actuating means for selectively and automaticallycontrolling functional operations in keyboard printers and the like in adependable and highly efficient manner.

It is another object of the present invention to provide forelectromagnetic actuating means which is directly engageable with theend of each interposer in the operational control linkage in order tocontrol a functional operation in a keyboard printer, such as, thefunctions of tab," space," backspace," index and return," toautomatically but selectively release the interposer in response to anapplied electrical signal, and to closely follow return movement of theinterposer to its latched position.

It is a further object of the present invention to provide anoperational input assembly for a keyboard printer in which the mass andsize of armature control plates are minimizedand adjustable actuatingrods are responsive to movement of the armature plates to operate uponthe ends of operational interposers to release same in performingselected functional operations, and, when deenergized, the rods andplates will follow return movement of the interposers to their originallocked positions in preparation for the next functional operation.

In accordance with the present invention, an electromagnetic actuatingdevice controls functional operations of a keyboard printer through anarmature plate and a threadedly adjustable actuator rod directlyengageable with a pivotal latch at the free end of an interposer. Thelatch, being normally secured, latches the interposer in an inoperativeposition and is pivotal away from the latched position to free theinterposer to carry out a desired function. Typical of the interposerconstruction is that utilized for manual selection in the IBM Selectrictypewriter which has an interposer manually engageable to release anassociated pivotal latch. In the present invention, the interposer andassociated latch are selectively released in response to an electricalcontrol signal applied to a solenoid for each operation to be performed.The solenoids are mounted in a common open housing, and a flat,lightweight armature plate for each interposer is extended across theopen end of the housing, the plate extending loosely through slots inopposite sides of the housing, and the actuator rod extends from theopposite end for engagement with the free end of the latch. Each plateoperates on an interposer through its actuator rod in releasing thelatch, and the rod remains in contact with the latch in following returnmovement of the interposer to the original locked position.

The above and other objects, advantages and features of the presentinvention will become more readily appreciated and understood from aconsideration of the following detailed description when taken togetherwith the accompanying drawing, in which:

FIG. 1 is a perspective view of the preferred form of operational inputmechanism in accordance with the present invention, the mechanism shownmounted on the underside of a typewriter but illustrated in a positionrotated counterclockwise.

FIG. 2 is a top plan view of the preferred form of operational inputmechanism.

FIG. 3 is a side elevational view illustrating the relative dispositionbetween parts comprising the operational input mechanism.

FIG. 4 is a view in detail of the latch and actuating rod portions ofthe operational input mechanism; and

FIG. 5 is a fragmentary sectional view fo the latch mounting in theframe taken along line 5-5 of FIG. 3.

Referring in more detail to the drawing, there is shown by way ofillustrative example in FIGS. 1 to 5 a preferred form of operationalinput control mechanism which is particularly adaptable for use incontrolling the functional operations of a keyboard printer, forexample, of the type referred to as an input/output typewriter. Atypical typewriter unit is the Selectric l/O Keyboard Printermanufactured by International Business Machines (IBM). The IBM Selectrichas a plurality of operational modes including index," tab, carrierreturn, space" and backspace and in manual keyboard operations eachfunctional operation is activated by a separate operational interposeror control lever, a portion of which is designated at 10 in FIG. 3. Eachoperational interposer 10 includes an elongated, slidable arm member 12provided with a pivotal latch 13 which is pivotal about a pivot pin 14inwardly of the free end of the interposer l0 and is provided with ashoulder or ledge 15, shown in detail in FIG. 4. Normally, the latch 13is biasedby a spring element 16 into an inoperative position byengagement of the shoulder 15 with a stationary latch plate 17. Theouter extremity 18 of the interposer I0 is also provided with adownwardly inclined, laterally extending or bent tab portion 19 which inmanual operations is selectively engaged by a bent portion 20 on amanual release member, here represented at R, so as to effect pivotalmovement of the interposer 10 about its opposite pivotal end, not shown,until the shoulder 15 clears the latch plate 17 and the interposer 10 isfree to slide longitudinally in the direction of the arrow to initiate aselected functional operation through the control mechanism of theprinter. Thus, an operational interposer l0 and associated latch 13 andrelease mechanism R is provided for each functional operation and eachis independently controllable to select its corresponding functionaloperation all in a well-known manner. Moreover, in manual operations,the operational interposers 10 selected in performing given functionaloperations are returned to their original disposition at the end of theoperating cycle and the latch 13 automatically returned to its latchdisposition by the return spring 16; and in turn the release members Rare reset by a reset bail 22 which is pivotal about a shaft 23 journaledat opposite ends in spaced carrier brackets 24. One end of the shaft 23is connected to a pivot arm 25 whose opposite end is secured by clevis26 to a control rod 27 operated off of a timing switch, not shown, butwhich is set forth and described in more detail in my copendingapplication for patent, Ser. No. 75,982, filed Sept. 28, 1970, andassigned to the assignee of the present invention. In a manner notshown, the control rod 27 will cause outward pivotal movement of thereset bail 22 against extensions R of the release members R to returnthe release members R to their original dispositions.

When the Selectric Keyboard Printer is energized automatically to printout information from a remote station, such as, a reader, by thetransmission of electrical signals representing the information to theprinter, the operational input control or selector mechanism of thepresent invention similarly must be selectively controlled to performfunctional operations in correlation with the matter being printed. Tothis end, signalresponsive means comprises a series of operational inputsolenoids 28 which, as shown in FIGS. 2 to 4, are arranged inside-by-side relation to one another in a common, generally U-shapedhousing 29 which is attached by a mounting bracket 30 to frame portion31 of the typewriter. As illustrated, the housing 29 is in the form of agenerally U-shaped channel having a closed end portion 32 and oppositesides 33 and 34 with the side portion 33 suitably attached by connectingscrews 35 to the mounting bracket 30, the latter extendingperpendicularly from its connection to the frame 31. In connectedrelation,,-the open end of the housing 29'is in the facing relation tothe frame portion 31 and the side portion 34 of the housing 29 includesan extension plate 37 mounted by connecting screws 38 to the externalsurface of the side portion 34.

A plurality of solenoids 28 are mounted in the solenoid housing 29, onefor each functional operation to be performed, and the solenoids 28 arearranged with their pole pieces 40 projecting from the open end of thechannel in facing relation to the frame 31, each of the solenoids 28adapted to independently control unlatching of an operational interposerthrough latch control means generally designated at 42 and presently tobe described. The latch control mechanism 42 for each operationalinterposer l0 and associated latch 13 includes an armature plate 44which is mounted on the solenoid housing 29 for extension across theexposed end of each pole piece 40. Aligned pairs of slots 45 and 46 areexposed at spaced intervals along the length of opposite sides 33 and 34of the solenoid housing, there being a seriesof slots 45 at spacedintervals in the side 33 of the housing 29 and a plurality of slots 46at correspondingly spaced intervals along the extension plate 37outwardly of the free or open end of the side portion 34. Each armatureplate 44 is relatively flat and elongated foriextension from a seatingslot 30 through an aligned pair of slots 45 and 46 with one end of thearmature plate notched as at 48 to be loosely secured within a slot 45.The intermediate part of each plate 44 extends through a slot 46 and anoutward extension 49 projects beyond the housing 29 in spaced parallelrelation to an interposer 10. The outermost extremity of the armatureplates 44 terminate in a laterally offset portion 50 which is alignedopposite to the latch 13 of its respective interposer 10 and serves as asupport for an actuator rod or control arm 52 extending normal to theplate 44. Each actuator rod 52 has a threaded end 53 passed through anaperture 51 in the offset portion 50 which is adjustably secured by apair of lock nuts 54 and 55; and further the opposite end of the rod 52is in the form of a generally U-shaped or hooked end portion 56 which ispassed over the end of the latch 13 and into engagement with the latch13 directly behind its shoulder 15.

As illustrated in FIGS. 1 and 2, when an electrical signal is applied toeach solenoid coil, energization of the solenoid 28 will cause itsarmature plate 44 to be drawn inwardly toward the pole piece 40. Theactuator rod 52 will follow movement of the plate 44 to draw the latch13 away from its latched position with respect to the latch plate 17 andpermit slidable movement of the interposer 10 as described. Theparticular distinct advantages in utilizing the actuator rod 52 asdisclosed and illustrated are that it minimizes the size and weight ofthe entire mechanism as well as the number of adjustments required inmounting the operational input control mechanism on the printer unit,since the hooked end portion 56 of the rod 52 simply can be passed overthe end of the latch 13 into position behind the shoulder l5 and itsthreaded end 53 tightened to draw the hooked end portion 56 against theunderside of the latch 13 when the armature plate 44 is normallydisposed away from the solenoid 28. In addition, the armature plate 44will closely follow return movement of the latch l3'to its latchedposition, under the urging of the spring 16 at the end of eachoperational cycle, thereby obviatingthe use of a special returnmechanism for the armature plate 44 and latch control rod 52.

When the input control mechanism is installed, the mounting bracket 30is first attached to the frame 31 and the solenoid housing 29 affixed tothe bracket 30 with the armature plates 44 extending in spaced parallelrelation to the interposers l0 and the rods 52 secured to the latches13. The desired close adjustment is afforded through tightening of theactuator rods 52 by the lock nuts 54 and 55, and enlarged slots, notshown, may be provided on the mounting bracket 30 for adjustableattachment between the bracket 30 and side portion 33 of the housing 29so that the proper spacing is established between the armature plates44, solenoid cores 28 and the ends of the interposers 10. Further, it isdesirable to apply a strip of plastic 60 over the exposed ends of thepole pieces 40 to minimize effects of residual magnetism and this strip60 may suitably be composed of Mylar or Teflon to maintain the necessaryair gap between the plates 44 and pole pieces 40. In addition, a fluxreturn path is established between the solenoid housing 29 andtypewriter through the mounting bracket 30 to the frame 31. When anelectrical signal is applied to any one or more of the solenoids 28, theassociated armature plate 44 is drawn inwardly against the core of thesolenoid 28 to draw the latch l3 away from the latch plate 17 and permitthe interposer to be activated to perform the desired functionaloperation. Any one or more desired func tional operations may beeffected simultaneously; and, as previously stated, at the end of theoperational cycle each activated interposer l0 10 will automaticallyreset its associated armature plate 44 to the original disposition awayfrom the solenoid 28 in preparation for the next functional operation.The slots 45, 46 are dimensioned to prevent lateral displacement of thearmature plates 44 while permitting the plates 44 to rock the limiteddistance necessary to control movement of the ac tuator rods 52, the endof the side portion 34 limiting inward movement of the plates 44 to theextent necessary to release the latch 13.

From the foregoing, it will be evident that the operational inputcontrol mechanism of the present invention employs a relativelylightweight latch control means which greatly minimizes the size andweight of the armature plates 44 and rods 52 as well as the amount ofmovement or throw" necessary to release a selected interposer 10. Thisis important in reducing the force curve of the solenoid 28 whichincreases sharply with increases in the amount of throw or movement ofthe armature plate 44. Additionally, closer adjustment is affordedthrough independent adjustability of the actuator rods 52 which againoperate upon the pivotal latch members 13, as opposed to the end of theinterposer l0, and are not affected by and do not interfere with themanual operation of the printer unit.

It is therefore to be understood that various modifications and changesmay be made in the detailed construction and arrangement of partscomprising the preferred form of the present invention without departingfrom the spirit and scope thereof.

1 claim:

1. In -a keyboard printer having a plurality of operational controlinterposers arranged in closely spaced,

juxtaposed relation to one another, each operational control interposerhaving a free end and being independently swingable from a normallyinoperative position to an operative position to perform a selectedfunctional operation, each operatiorial control interposer having apivotal latch member provided with a free end spaced inwardly of thefree end of said interposer and engageable with a stationary latch plateto releasably latch the operational control interposer against movement,a spring return member connected between each said operational controlinterposer and said pivotal latch member biased to urge the pivotallatch member into engagement with the latch plate whereby to latch theinterposer in the inoperative position, an operational input mechanismfor selectively effecting release of each of said pivotal latch membersfrom said latch plate in controlling each of a plurality of functionaloperations, said mechanism comprising:

electromagnetic actuating means including a common housing mounted onsaid printer with an open end of said housing aligned in spaced, facingrelation to said interposers, and a plurality of solenoids in saidhousing disposed in closely spaced, juxtaposed relation, there being asolenoid for each of said interposers, an armature plate for each ofsaid solenoids disposed across the open end of said housing in spaced,substantially parallel relation to one of said interposers, eacharmature plate loosely disposed in slots in opposite sides of saidhousing for movement toward and away from said interposers under theinfluence of said solenoids and each armature plate extending beyondaslot in one side of the housing to terminate in a free end aligned inspaced relation to a respective pivotal latch member, and

an actuating rod extending normally from each armature plate includingone end adjustably connected to the free end of said armature plateexternally of said housing, the opposite end of each actuating rodengageable with each pivotal latch member inwardly of the free end ofeach associated interposer for selectively releasing the pivotal latchmember when an associated solenoid is energized and the armature plateis moved away from the interposer in advancing the interposer from theinoperative to the operative position upon energization of eachassociated solenoid, and the interposer being returned to theinoperative position and the pivotal latch member engaging the latchplate to cause the actuating rod to move the armature plate toward theinterposer solely under the urging of said spring return member wheneach associated solenoid is deenergized.

2. In a keyboard printer according to claim I, the opposite end of saidactuating rod having a bent leverengaging portion engageable with thepivotal latch member.

3. In a keyboard printer according to claim 2, the one end of saidactuating rod being threaded for extension through an opening in saidfree end of said armature plate beyond the side of said common housing,and lock nuts threadedly disposed on the threaded end of said actuatingrod to position the lever-engaging portion of said actuating rod inengagement with the annature plate, and the opposite end of saidactuating rod having said bent lever-engaging portion formed as agenerally U-shaped return disposed for engagement with said pivotallatch member.

4. In a keyboard printer according to claim 1, each armature plate beingrockable about the edge of the slot most removed from said actuatingrod, and a plastic tape covering the ends of said solenoids beneath saidarmature plate. flat and elongated for extension from a seating slot 30'through an aligned pair of slots and 46 with one end of the armatureplate notched as at 48 to be loosely secured within a slot 45. Theintermediate part of each plate 44 extends through a slot 46 and anoutward extension 49 projects beyond the housing 29 in spaced parallelrelation to an interposer 10. The outermost extremity of the armatureplates 44 terminate in a laterally offset portion 50 which is alignedopposite to the latch 13 Of its respective interposer 10 and serves as asupport for an actuator rod 94 control arm 52 extending normal to theplate 44. Each actuator rod 52 has a threaded end 53 passed through anaperture 51 in the offset portion 50 which is adjustably secured by apair of lock nuts 54 and 55; and further the opposite end of the rod 52is in the form of a generally U-Shaped or hooked end portion 56 which iSpassed over the end of the latch 13 and into engagement with the latch13 directly behind its shoulder 15.

As illustrated in FIGS. 1 and 2, when an electrical signal is applied toeach solenoid coil, energization of the solenoid 28 will cause itsarmature plate 44 to be drawn inwardly toward the pole piece 40. Theactuator rod 52 will follow movement of the plate 44 to draw the latch13 away from its latched position with respect to the latch plate 17 andpermit slidable movement of the interposer 10 as described. Theparticular distinct advanttages in utilizing the actuator rod 52 asdisclosed and illustrated are that it minimizes the size and weight ofthe entire mechanism as well as the number of adjustments required inmounting the operational input control mechanism on the printer unit,since the hooked end portion 56 of the rod 52 simply can be passed overthe end of the latch 13 into position behind the shoulder '15 and itsthreaded end 53 tightened to draw the hooked end portion 56 against theunderside of the latch 13 when the armature plate 44 is normallydisposed away from the solenoid 28. In addition, the armature plate 44will closely follow return movement of the latch 13 to its latchedposition, under the urging of the spring 16 at the end of eachoperational cycle, thereby obviating the use of a special returnmechanism for the armature plate 44 and latch control rod When the inputcontrol mechanism is installed, the mounting bracket 30 is firstattached to the frame 31 and the solenoid housing 29 affixed to thebracket 30 with the armature plates 44 extending in spaced parallelrelation to the interposers l and the rods 52 secured to the latches 13.The desired close adjustment is afforded through tightening of theactuator rods 52 by the lock nuts 54 and '55, and enlarged slots, not

shown, may be provided on the mounting bracket 30 for adjustableattachement between the bracket 30 and side portion 33 of the housing 29so that the proper spacing is established between the armature plates44, solenoid cores 28 and the ends of the interposers 10. Further, it isdesirable to apply a strip of plastic 60 over the exposed ends of thepole 40 to minimize effects of residual magnetism and this strip 60 maysuitably be composed of Mylar or Teflon to maintain the necessary airgap between the plates 44 and pole pieces 40. in addition, a flux returnpath is established between the solenoid housing 29 and typewriterthrough the mounting bracket 30 to the frame 31. When an electricalsignal is applied to any one or more of the solenoids 28, the associatedarmature plate 44 is drawn inwardly against the core of the solenoid 28to draw the latch 13 away from the latch plate 17 and permit theinterposer to be activated to perform the desired functional operation.Any one or more desired functional operations may be effectedsimultaneously; and, as previously stated, at the end of the operationalcycle each activated interposer l0 10 will automatically resetitsassociated armature plate 44 tothe original disposition away ynemthesolenoid 28 in preparation for the next functional operation. The slots45, 46 are dimensioned to prevent lateral displacement of the armatureplates 44 while permitting the plates 44 to rock the limited distancenecessary to control movement of the actuator rods 52, the end of theside portion 34 limiting inward movement of the plates 44 to theextentnecessary to release the latch 13.

From the foregoing, it will be evident'that the operational inputcontrol mechanism of the present invention employs a relativelylightweight latch control means which greatly minimizes the sizean'dweight of the armature plates 44 and rods 52 as well as the amountof movement or thrownecessary to release a selected interposer 10. Thisis important in reducing the force curve of the solenoid 28 whichincreases sharply with increases in the amount of throw or movement ofthe armature plate 44. Additionally, closer adjustment is affordedthrough independent adjustability of the actuator rods 52 which againoperate upon the pivotal latch members 13, as opposed to the end of theinterposer l0, and are not affected by and do not interfere with themanual operatio of the printer unit It is therefore to be understoodthat various modifications and changes may be made in the detailedconstruction and arrangement of parts comprising the preferred Form ofthe present invention without departing from the spirit and scopethereof.

1 claim:

1. In a keyboard printer having a plurality of operational controlinterposers arranged in closely spaced, juxtaposed relAtion to oneanother, each opPrational control interposer having a free end and beingindependentl swingable from a normally inoperative position to anoperative position to perform a selected functional operation, eachoperational control interposer having a pivotal latch member providedwith a free end spaced inwardly of the free end of said interposer andengageable with a stationary latch plate to releasably latch theoperational control interposer against movement, a spring return memberconnected between each said operational control interposer and saidpivotal latch member biased to urge the pivotal latch member intoengagement with the latch plate whereby to latch the interposer in theinoperative position, an operational input mechanism for selectivelyeffecting release of each of said pivotal latch members from said latchplate in controlling each of a plurality of functional operations, saidmechanism comprising:

electromagnetic actuating means including a common housing mounted onsaid printer with anopen end of said housing aligned in spaced, facingrelation to said interposers, and a plurality of solenoids in saidhousing disposed in closely spaced, juxtaposed relation, there being asolenoid for each of said interposers,

an armature plate for each of said solenoids disposed across the openend of said housing in spaced, substantially parallel relation to one ofsaid interposers, each annature plate loosely disposed in slots inopposite sides of said housing for movement toward and away from saidinterposers under the influence of said solenoids and each armatureplate extending beyond a slot in one side of the housing to terminate ina free end aligned in spaced relation to a respective pivotal latchmember, and

an actuating rod extending normally form each armature plate includingone end adjustably connected to the free end of said armature plateexternally of said housing, the opposite end of each actuating rodengageable with each pivotal latch member inwardly of the free end ofeach associated interposer foR selectively releasing the pivotal latchmember when an associated solenoid is energized and the armature plateis moved away from the interposer in advancing the interPoser from theinoperative to the operative position upon energization of eachassociated solenoid, andthe interposer being retur0e o the inoperatve9to cause the actuating rod to move the armature plate toward theinterposer solely under the urging of said spring return member wheneach associated solenoid is deenergized.

ture plate, and the opposite end of said actuating rod having said bentlever-engaging portion formed as a generally U-shaped return disposedfor engagement with said pivotal latch member.

4. In a keyboard printer according to claim I each armature plate beingrockable about the edGe of the slot most removed from said actuatingrod, and a plastic tape covering the ends of said solenoids benPath saidarmature plate.

1. In a keyboard printer having a plurality of operational controlinterposers arranged in closely spaced, juxtaposed relation to oneanother, each operational control interposer having a free end and beingindependently swingable from a normally inoperative position to anoperative position to perform a selected functional operation, eachoperational control interposer having a pivotal latch member providedwith a free end spaced inwardly of the free end of said interposer andengageable with a stationary latch plate to releasably latch theoperational control interposer against movement, a spring return memberconnected between each said operational control interposer and saidpivotal latch member biased to urge the pivotal latch member intoengagement with the latch plate whereby to latch the interposer in theinoperative position, an operational input mechanism for selectivelyeffecting release of each of said pivotal latch members from said latchplate in controlling each of a plurality of functional operations, saidmechanism comprising: electromagnetic actuating means including a commonhousing mounted on said printer with an open end of said housing alignedin spaced, facing relation to said interposers, and a plurality ofsolenoids in said housing disposed in closely spaced, juxtaposedrelation, there being a solenoid for each of said interposers, anarmature plate for each of said solenoids disposed across the open endof said housing in spaced, substantially parallel relation to one ofsaid interposers, each armature plate loosely disposed in slots inopposite sides of said housing for movement toward and away from saidinterposers under the influence of said solenoids and each armatureplate extending beyond a slot in one side of the housing to terminate ina free end aligned in spaced relation to a respective pivotal latchmember, and an actuating rod extending normally from each armature plateincluding one end adjustably connected to the free end of said armatureplate externally of said housing, the opposite end of each actuating rodengageable with each pivotal latch member inwardly of the free end ofeach associated interposer for selectively releasing the pivotal latchmember when an associated solenoid is energized and the armature plateis moved away from the interposer in advancing the interposer from theinoperative to the operative position upon energization of eachassociated solenoid, and the interposer being returned to theinoperative position and the pivotal latch member engaging the latchplate to cause the actuating rod to move the armature plate toward theinterposer solely under the urging of said spring return member wheneach associated solenoid is deenergized.
 2. In a keyboard printeraccording to claim 1, the opposite end of said actuating rod having abent lever-engaging portion engageable with the pivotal latch member. 3.In a keyboard printer according to claim 2, the one end of saidactuating rod being threaded for extension through an opening in saidfree end of said armature plate beyond the side of said common housing,and lock nuts threadedly disposed on the threaded end of said actuatingrod to position the lever-engaging portion of said actuating rod inengagement with the armature plate, and the opposite end of saidactuating rod having said bent lever-engaging portion formed as agenerally U-shaped return disposed for engagement with said pivotallatch member.
 4. In a keyboard printer according to claim 1, eacharmature plate being rockable about the edge of the slot most removedfrom said actuating rod, and a plastic tape covering the ends of saidsolenoids beneath said armature plate.